Chart C-12C Coolant Fan Control Circuit

Chart C-12C:

A/C Circuit:

CIRCUIT DESCRIPTION:
Power for the coolant fan motor comes through the fusible link to terminal "30" on the relay. The relay is energized when current flows to ground through the quad driver module inside the ECM.

Coolant fan Relay - The coolant fan relay is energized by the ECM. The ECM energizes the relay through terminal "YE8" when the coolant temperature reaches 100°C (212°F). The fan relay is also energized when A/C is requested.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Removing the relay interrupts current flow to the fan motor so the fan should not be "ON."

2. Test light should be "OFF" with coolant temperature below 100°C (212°F) no DTC 14 or 15, and A/C "OFF" (no A/C request).

3. If the test light goes "OFF" when the black C-D connector is disconnected, the ECM is faulty and has to be replaced.

DIAGNOSTIC AIDS:
If fan operates normally but an overheat condition exists, refer to Engine Coolant Temperature Sensor "Temperature vs. Resistance Values" table on DTC 14 chart. Replace sensor if faulty.